Radeon X300 Series Users Guide for reference:http://www.fujitsu-siemens.co.uk/rl/serv.../RadeonX300.pdf
Excerpt of the Radeom X300 specs from http://ati.amd.com/products/radeonx300/specs.html
Seamless integration of pixel shaders with video in real time
FullStream™ video de-blocking technology for Real, DivX, and WMV9 formats
VideoSoap™ noise removal filtering for captured video
MPEG1/2/4 decode and encode acceleration
Hardware Motion Compensation, iDCT, DCT and color space conversion
All-format DTV/HDTV decoding
YPrPb component output for direct drive of HDTV displays†
Adaptive Per-Pixel De-Interlacing and Frame Rate Conversion (temporal filtering
† Please check with your graphics board manufacturer for HDTV adapter support
Unfortunately there is no way to check the internet to see if a simple adapter will work in your situation without knowing the actual video card or motherboard. If you know the card/motherboard manufacturer I would do as suggested above and contact them to see if it has HDTV adapter support.
If you can’t contact the card manufacture you could try this adapter and return it if it doesn’t work:http://sewelldirect.com/dvivideoadapter.asp
If a DVI to component adapter doesn’t work then you are left with a few options only two of which I would consider.
1. Get a video card that has some native or adapter based support for component output. If you do go with one of these cards (sorry no suggestions since I’ve never researched them) note that they sometimes have display issues like over-scanning. So make sure to read reviews.
2. Live with what you have until you’re ready to get another HDTV.
I wouldn't waist my money on a VGA to Component adapter since for about the same money you could just update your video card.